58 THE APODID^ parti 



sensory organs which are now called auditory really 

 serve for regulating the position of the body in the 

 water. The position of the organ in Apus seems to 

 support this view. The feathered hairs fringing the 

 flabeila are far more capable of appreciating and 

 responding to sound waves than is a plexus of pig- 



FiG. 36. — Nauplius of Z. prodiichcs from the side (after Brauer), showing the position 

 of the eyes at the frontal end, i.e. in their passage from the ventral to the dorsal 

 position. 



ment cells in a closed vessel suspended inside the 

 body some distance beneath the outer integument. 

 There is here, however, abundant room for further 

 research. It is possible that in the course of the 

 development of some Entomostraca, its original 

 function as a directive body may entirely give place 

 to secondary visual functions, or, as above suggested. 



